To make a signature you're going to need a program such as Photoshop or Gimp. However, in this case, it would most likely best to go with Gimp seeing as Photoshop costs quite a bit to purchase. However, if you don't feel like downloading/purchasing either program you could always request a sig in the request a signature thread.

1. At the top of the site there should be a "User CP" on the left. Click it!
2. Look to the left and under the Control Panel
3. find a section called "Settings & Options" which should be the first and find "Edit Signature" and click it.
4. Write whatever you want and when you are done go down and press "Save Signature"

Also if you want to add an image...
1. Find an Image that you want( has to be 500 width by 130 height)
2. Right click the image>Properties
3. Copy the Location/URL
4. Go edit your signature and click this icon where the tools are.... .
5. Paster the Url and click OK.
6. Now the picture you want will show up as a URL with this around it . When you save it you will have the image up.